A-label definition

[Mark Andrews]

> Mark Andrews wrote:
> 
> > At best there is guidance not to allocate a TLD which will
> > potentially clash with a representation of a IPv4 address.
>  
> > 0xde.0xad.0xbe.0xef
> > 222.137.190.239
> > 0xdeadbeef
> > 0337.0211.0276.0357
> > 033653337357
> > 3735928559
> 
> The 0x concept would break various of my scripts based on 
> "if it only contains the characters '0.123456789' it might
>  be an IPv4, and it is no FQDN (or vice versa)".  
> 
> Maybe it is a good idea to say that  "0x" 1*HEXDID  cannot
> be a <toplabel>, but that has to be said in something that
> is fresher than "RFC 952 - status: unknown".  With no note
> about "updated by RFC 1123".
> 
> > xn--* will never clash with a dotted decimial or any other
> > representation of a IPv4 address.
> 
> Yes, any valid A-label is automatically a valid <toplabel>.
> 
> > xn--* is a legal tld under RFC 952 and it was not made
> > illegal by RFC 1123.
> 
> RFC 952 has a limit of 24 characters and proposes suffixes
> like "-GW" and "-NIC", let's say it was not designed for
> IDNA and RFC 3492.  If you think it helps we could move
> RFC 952 to HISTORIC, it muddies the water when it shows up
> in ICANN documents published in 2008.
> 
> The decruft experiment (RFC 4450) missed RFC 952, because 
> it was limited to standards, excluding "status: unknown".

	It is the current RFC that limits hostnames to LDH.  -GW
	and -NIC etc. are just shoulds not musts.

	To move RFC 952 to historic we need to write a RFC which
	consolidates all the changes to hostnames: syntax, lengths
	etc. into one document.

>  Frank
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org